Cathode-grid assembly for a cathode ray tube

ABSTRACT

A cathode-grid assembly for a cathode ray tube comprises a substantially cup shaped grid having a closed end containing a substantially centrally located aperture and a projecting contiguous side wall. The closed end and the side wall define a hollow interior. A cathode and a cathode support are positioned and fixed within the hollow interior of the grid. The cathode comprises a hollow metallic sleeve closed at one end by a cathode cap the outermost surface of which contains an electron emissive material. The cathode support comprises an electrically insulating member of a size to fit within the hollow interior of the grid and has upper and lower surfaces. A substantially centrally located cathode aperture interconnects the upper and lower surfaces of the support. First means extend from the lower surface of the support for mounting the support within the hollow interior of the grid and second means also extend from the lower surface of the support for mounting the cathode.

United States Patent [191 Kerstetter CATHODE-GRID ASSEMBLY FOR A CATHODERAY TUBE [75] Inventor: Donald R. Kerstetter, Emporium,

[73] Assignee: GTE Sylvania Incorporated,

Stamford, Conn.

[22] Filed: Mar. 6, 1974 [21] Appl. No.: 448,681

Primary Examiner-Robert Segal Attorney, Agent, or FirmNorman .1.OMalley; William H. McNeill; Cyril A. Krenzer 1 May 20, 1975 {57}ABSTRACT A cathode-grid assembly for a cathode ray tube comprises asubstantially cup shaped grid having a closed end containing asubstantially centrally located aperture and a projecting contiguousside wall. The closed end and the side wall define a hollow interior. Acathode and a cathode support are positioned and fixed within the hollowinterior of the grid. The cathode comprises a hollow metallic sleeveclosed at one end by a cathode cap the outermost surface of whichcontains an electron emissive material. The cathode support comprises anelectrically insulating member of a size to fit within the hollowinterior of the grid and has upper and lower surfaces. A substantiallycentrally located cathode aperture interconnects the upper and lowersurfaces of the support. First means extend from the lower surface ofthe support for mounting the support within the hollow interior of thegrid and second means also extend from the lower surface of the supportfor mounting the cathode.

7 Claims, 2 Drawing Figures CATHODE-GRID ASSEMBLY FOR A CATHODE RAY TUBEBACKGROUND OF THE INVENTION This invention relates to cathode ray tubecathodes and more particularly to a grid-cathode assembly for use withcathode ray tubes. Cathode ray tube cathodes of a current designcomprise a cylindrical cathode which is welded to a heavy massivemetallic eyelet which is in turn welded to a cathode support which isembedded into glass beads which align and maintain the cathode andseveral other grids. Such a cathode system is forced to utilize severallong connections for supporting the grid and cathode and permitspossible movement between these two elements. Prior art suggestions havealso employed a cathode mounted within the cup shaped Gl grid of anelectron gun. Such systems usually employed a ceramic disc having aplurality of metal rings brazed thereto. Spacers were also provided forpositioning the ceramic disc within the GI. Such assemblies wereexpensive because of the machined ceramic disc and because of thenecessity of brazing or using glass to metal sealing elements to at tachthe metal components to the ceramic disc. It would be at an advance inthe art if a simple, rugged and economical cathode structure could beprovided.

OBJECTS AND SUMMARY OF THE INVENTION It is. therefore. an object of thisinvention to obviate the disadvantages of the prior art.

It is another object of this invention to enhance cathode mounting.

Yet another object of the invention is the provision of a simple, yetrugged and economical cathode support.

These objects are accomplished in one aspect of the invention with theprovision of a cathode-grid assembly for a cathode ray tube whichcomprises a substantially cup shaped grid having a closed end containinga sub stantially centrally located aperture and a projecting contiguousside wall. The closed end and side wall de' fine a hollow interior. Acathode and a catohde support are positioned within the hollow interiorand firmly and ruggedly affixed thereto. The cathode comprises a hol lowmetallic sleeve closed at one end by a cathode cap the outermost surfaceof which contains an electron emissive material. The cathode supportcomprises an electrically insulating member of a size to fit within thehollow interior of the grid and which has upper and lower surfaces. Asubstantially centrally located cathode receiving aperture interconnectsthe upper and lower surfaces. First means extend from the lower surfacefor mounting the support within the hollow interior of the grid andsecond means also extend from the lower surface of the support formounting the cathode. This structure is rugged and simple and obviatesthe disadwmtages of the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational sectionalview shown in sirnplified form of the cathode-grid assembly of theinvention; and

FIG. 2 is a plan view of the cathode-grid assembly shown in FIG. I.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding ofthe present invention together with other and further objects,advantages and capabilities thereof, reference is made to the followingdisclosure and appended claims in conjunction with the abovedeseribeddrawings.

Referring now to the drawings with greater particularity. there is shownin FIG. 1 a cathode-grid assembly 10 for a cathode ray tube. Thecathode-grid assembly 10 comprises a substantially cup shaped grid 12having a closed end 14 and a projecting contiguous side wall 16. Asubstantially centrally located aperture 18 is pro vided in closed end14. The closed end 14 and contiguous wall 16 define a hollow interior20. Positioned within the hollow interior 20 are a cathode 22 and acathode support 24. The cathode comprises a hollow metallic sleeve 26closed at one end by a cathode cap 28. The outermost surface of cap 28contains an elec tron emissive material 30. The cathode support 24 iscomprised of an electrically insulating member 32 of a suitable materialsuch as glass. The electrically insulating member 32 is of a size to fitwithin the hollow interior and it has upper and lower surfaces 34 and 36respectively. A centrally located cathode aperture 38 is provided whichinterconnects the upper and lower surfaces. A first means 40 extendsfrom the lower surface 36 of insulating member 32 to provide formounting of the support 32 within the hollow interior 20 of grid 12.Also projecting from the bottom surface 36 are second means 42 formounting the cathode 22.

The first means 40 comprises a plurality of rodlike metal elements 44which have one end inserted and firmly affixed in electricallyinsulating member 32 and which project longitudinally therefrom alongthe longitudinal axis of the cathode and outwardly therefrom away fromthe longitudinal axis to provide a terminal portion 46 which attaches tothe inside of the grid 12. By referring to FIG. 2 it will be seen thatthere are at least three rodlike metallic elements 44 and that they aresubstantially equidistantly spaced apart.

The second means 42 also comprises a plurality of rodlike members 48which also have one end mounted within electrically insulating member 32and which extend longitudinally therefrom along the longitudinal axis ofthe cathode and have a terminal portion 50 formed to extend inwardlytoward the longitudinal axis of the cathode. The terminal portion 50 ofthe rodlike elements 48 is flattened to provide an attaching surface forthe bell shaped bottom portion 52 of cathode 22.

Again. referring to FIG. 2, it will be seen that the rodlike elements 48of second means 42 are also at least three in number and aresubstantially equidistantly spaced apart. Further, it will be seen thateach of the rodlike elements 48 of the second means 42 is positionedsubstantially equidistantly between two of the rodlike elements 44 ofthe first means 40.

It will be seen from the above that an extremely rugged yet simplecathode-grid assembly is provided. The electrically insulating member32, being formed of glass and having the first and second support meansinserted therein allows that this structure can be fabricated onconventional electron tube stem making equipment. The cathode structureremains the same as that normally used with the prior art eyeletconstruction and thus further contributes to the low cost of the 3device. No changes are necessary in the grid [2 which can be aconventional Gl assemblyv Because the cath ode 22 is mounted within thegrid. one of the prime areas for misalignment is avoided.

While there have been shown what are at present considered to be thepreferred embodiments of the in vention it will be apparent to thoseskilled in the art that various changes and modifications can be madeherein without departing from the scope of the inven tion as defined bythe appended claims.

What is claimed is:

l. A cathode-grid assembly for a cathode ray tube comprising:

a substantially cup-shaped grid having a closed end containing asubstantially centrally located aperture and a projecting contiguousside wall, said closed end and said side wall defining a hollow interim;and

a cathode and a cathode support positioned within said hollow interior;

said cathode comprising a hollow metallic sleeve closed at one end by acathode cap the outermost surface of which contains an electron emissivematerial;

said cathode support comprising an electrically insulating member of asize to fit within said hollow interior and having upper and lowersurfaces;

a substantially centrally located cathode aperture in- 4 terconnectingsaid upper and lower surfaces and first and second means extending fromsaid lower surface for respectively mounting said support within saidhollow interior and for mounting said cathode.

2. The assembly of claim 1 wherein said first means for mounting saidsupport comprises:

a plurality of rod-like metallic elements inserted in said support andextending longitudinally and outwardly therefrom.

3. The assembly of claim 1 wherein said second means for mounting saidcathode comprises:

a plurality of rod-like metallic elements inserted in said support andextending longitudinally and inwardly therefrom.

4. The assembly of claim 3 wherein the terminal portion of said secondmeans is flat.

5. The assembly of claim 2 wherein said rod-like elements of said firstmeans are three in number and substantially equidistantly spaced.

6. The assembly of claim 3 wherein said rod-like ele ments of saidsecond means are three in number and substantially equidistantly spaced.

7. The assembly of claim 6 wherein each of said rodlike elements of saidsecond means is positioned substantially equidistantly between two ofsaid rod-like el' ements of said first means.

1. A cathode-grid assembly for a cathode ray tube comprising: asubstantially cup-shaped grid having a closed end containing asubstantially centrally located aperture and a projecting contiguousside wall, said closed end and said side wall defining a hollowinterior; and a cathode and a cathode support positioned within saidhollow interior; said cathode comprising a hollow metallic sleeve closedat one end by a cathode cap the outermost surface of which contains anelectron emissive material; said cathode support comprising anelectrically insulating member of a size to fit within said hollowinterior and having upper and lower surfaces; a substantially centrallylocated cathode aperture interconnecting said upper and lower surfacesand first and second means extending from said lower surface forrespectively mounting said support within said hollow interior and formounting said cathode.
 2. The assembly of claim 1 wherein said firstmeans for mounting said support comprises: a plurality of rod-likemetallic elements inserted in said support and extending longitudinallyand outwardly therefrom.
 3. The assembly of claim 1 wherein said secondmeans for mounting said cathode comprises: a plurality of rod-likemetallic elements inserted in said support and extending longitudinallyand inwardly therefrom.
 4. The assembly of claim 3 wherein the terminalportion of said second means is flat.
 5. The assembly of claim 2 whereinsaid rod-like elements of said first means are three in number andsubstantially equidistantly spaced.
 6. The assembly of claim 3 whereinsaid rod-like elements of said second means are three in number andsubstantially equidistantly spaced.
 7. The assembly of claim 6 whereineach of said rod-like elements of said second means is positionedsubstantially equidistantly between two of said rod-like elements ofsaid first means.